The present invention relates to fluid ejection systems. More particularly, the invention relates to a fluid ejection and scanning system with photosensor activation of ejection elements.
The art of inkjet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, facsimile machines, and multi-function devices have been implemented with inkjet technology for producing printed media. Generally, an inkjet image is formed pursuant to precise placement on a print medium of ink drops emitted by an ink drop generating device known as an inkjet printhead assembly. An inkjet printhead assembly includes at least one printhead. Inkjet printers have at least one ink supply. An ink supply includes an ink container having an ink reservoir. The ink supply can be housed together with the inkjet printhead assembly, or can be housed separately. Some conventional inkjet printhead assemblies span over a limited portion of a page width, and are scanned across the page. The inkjet printhead assembly is supported on a movable carriage that traverses over the surface of the print medium and is controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controllers, wherein the timing of the application of the ink drops is intended to correspond to a pattern of pixels of the image being printed.
A page-wide-array (PWA) printhead assembly spans an entire pagewidth (e.g., 8.5 inches, 11 inches, A4 width) and is fixed relative to the media path. A PWA printhead assembly includes a PWA printhead with thousands of nozzles that span the entire page width. The PWA printhead assembly is typically oriented orthogonal to the paper path. During operation, the PWA printhead assembly is fixed, while the media is moved under the assembly. The PWA printhead assembly prints one or more lines at a time as the page moves relative to the assembly.
Each nozzle chamber in a PWA printhead assembly typically includes an ejection element, a chamber layer, and a substrate. When a firing resistor is used as the ejection element, the firing resistor is located within the chamber on the substrate. During operation, the nozzle chamber receives ink from an ink supply through an inlet channel. The firing resistor is then activated so as to heat the ink thereon and cause a vapor bubble to form. The vapor bubble then ejects the ink as a droplet through the nozzle, and onto a media (e.g., paper, transparency). Droplets of repeatable velocity, volume, and direction are ejected from respective nozzles to effectively imprint characters, graphics, and photographic images onto a media.
The ejection element in a PWA printhead assembly of the piezoelectric type typically includes a piezoceramic layer. The piezoceramic layer consists of a flexible wall to which is attached a piezoceramic material on the side exterior to the chamber. During operation, the nozzle chamber receives ink from an ink supply through an inlet channel. The piezoceramic material is then activated so as to deform the wall into the chamber. The pressure generated then ejects the ink as a droplet through the nozzle, and onto a media (e.g., paper, transparency). Droplets of repeatable velocity, volume, and direction are ejected from respective nozzles to effectively imprint characters, graphics, and photographic images onto a media.
Because of the large number of nozzles in a PWA printhead assembly, and because the assembly typically prints one or more page-wide lines at a time, there are substantially more timing and control signals generated at a given time than for a scanning type printhead assembly. To print multiple lines as opposed to multiple characters, the firing of thousands more nozzles has to be controlled. Signals have to be transmitted to the thousands more firing resistors of such nozzles.
In typical PWA inkjet printers, complex electronics and interconnects have been used to generate the necessary signals and route them to the appropriate locations. Some PWA inkjet printers use a flexible printed circuit (xe2x80x9cflex circuitxe2x80x9d) attached to a printhead assembly that includes signal paths for carrying signals from a print processor to addressed firing resistors.
There is also a desire to produce reliable, high-yield, page-wide-arrays in a cost effective manner.
One form of the present invention provides a fluid ejection and scanning system including a fluid ejection assembly. The assembly includes a first plurality of photosensors, and a first plurality of ejection elements. Each of the ejection elements is configured to cause fluid to be ejected when the ejection element is activated. Each one of the photosensors in the first plurality is coupled to a respective one of the ejection elements for activating the ejection element. A second plurality of photosensors captures image data to generate a digital image of a media. A first light source of the system emits a light beam. A control system scans the light beam across the printhead assembly and selectively illuminates the photosensors in the first plurality, thereby activating the ejection elements coupled to the illuminated photosensors.